Integrated circuits are made up of a number of active devices and passive devices. These devices are further interconnected together to form a functional circuit. Typical interconnect structures include lateral interconnections such as metal lines, and vertical interconnections such as via contacts. The density of active and passive devices in modern integrated circuits is significantly increased, and therefore the amount of interconnections is increased. Currently, wafer level chip scale packaging (WLCSP) is widely used because of its relatively simple processes. In a typical WLCSP, post-passivation interconnect (PPI) lines are formed over passivation layers which cover and protect integrated circuits. When the amount of interconnections is increased, the PPI lines in WLCSP become more complex.